Sputter Gas Damage in Nanolayered Pt/Co/Ir-based Synthetic Antiferromagnets for Top-Pinned Magnetic Tunnel Junctions

We examine the role of sputter damage on limiting the perpendicular magnetic anisotropy and interlayer exchange coupling in Pt/Co/Ir-based synthetic antiferromagnets, a key building block used in the microelectronics community for standalone and embedded magnetic random access memories. By replacing the more conventional Ar process gas with Kr or Xe, we reduce the energy of backscattered sputter gas ions bombarding the substrate from in excess of 100 eV to a few 10 s of eV. Reducing this kinetic bombardment is critical to avoid intermixing of this nanolayered functional heterostructure, with the constituent Pt, Co, and Ir layer thicknesses each below 1 nm. Our approach leads to a simultaneous enhancement in the perpendicular magnetic anisotropy (>2 × 106 J/m3) and interlayer exchange coupling energy (>3.5 mJ/m2). This advantageous improvement in perpendicular anisotropy and interlayer exchange coupling is evident on a 5 nm-thick Pt buffer layer and additionally on an MgO/CoFeB/Mo underlayers complex, showing that this method can improve the performance of both top- and bottom-pinned reference layers in perpendicular magnetic tunnel junction devices. These experimental findings may help advance the processing of conventional and synthetic antiferromagnetic devices for emerging spintronic memory technologies.